1. Field of the Invention
The present invention relates to an apparatus which outputs a signal in connection with the movement of an optical adjustment unit provided for an optical device such as a television camera system, and more particularly, to a movement signal generation apparatus which can be applied to a video production system such as a virtual system which combines live-action video with computer graphics.
2. Description of Related Art
Conventionally, in a television lens, optical adjustment units such as a zoom lens, a focus lens, an iris, and an extender are electrically or manually operated to cause an optical change in an object image. This can create a desired video scene. Such an optical adjustment unit is coupled to a potentiometer or a rotary encoder. The detection result of the position of the optical adjustment unit is used for servo drive or display of the position of the optical adjustment unit.
The television lenses include large lenses with high accuracy for use in studios and the like and handy-sized lenses with favorable portability for use outdoors or on a user's shoulder. For the large lenses, an encoder which outputs digital signals with two phases is used as a position detector of an optical adjustment unit. For the handy-sized lenses, a potentiometer which outputs an analog signal is typically used.
In recent years, Japanese Patent Laid-Open No. H06 (1994)-121280 has disclosed a system which is called a virtual system and combines live-action video with computer graphic video related to the live-action video. The system employs a television lens such as the large lens and the handy-sized lens as described above.
Such a virtual system receives a signal (representing a zoom position, a focus position and the like) from a position detector linked with an optical adjustment unit of a television lens. This allows a computer in the system to produce computer graphic images corresponding to the size and the focal point of the live-action images to provide combined video without a feeling of strangeness even when zooming or focusing is performed in real time.
FIG. 9 primarily shows the structure of a zoom system of a large lens which is used for a virtual system. In FIG. 9, reference numeral 100 shows a television lens, reference numeral 101 shows a CPU which is responsible for control of the television lens, reference numeral 102 shows a DA converter to which the CPU 101 writes a command value in driving zoom, and reference numeral 103 shows an power amplifier which amplifies the power of the command from the DA converter 102.
Reference numeral 104 shows a motor which is driven with the power amplifier 103, reference numeral 105 shows a zoom lens which is coupled to the motor 104 and is moved in an optical axis direction to provide variable magnification, and reference numeral 106 shows a zoom digital encoder which serves as a zoom position detector linked with the zoom lens 105. Reference numeral 120 shows a counter which counts pulse signals with two phases from the zoom digital encoder 106 and uses the resultant data as a zoom position.
While FIG. 9 shows the structure of the zoom system in the television lens, the structures for a focus lens, an iris, and an extender are the same as the zoom system.
With the structure, when a zoom drive command signal is input from a command apparatus (demand), not shown, connected to the television lens 100, the CPU 101 uses the zoom drive command signal and a current zoom position taken from an AD converter 108 to calculate a new zoom command position and writes the result to the DA converter 102, thereby enabling zoom position control.
Pulse signals with two phases from the zoom digital encoder 106 are input as a zoom position signal 301 to a virtual system 200, described next.
The virtual system 200 receives the pulse signals with two phases 301 which correspond to the zoom position signal from the television lens 100. Reference numeral 202 shows a counter which calculates the position of the zoom lens 105 from the zoom position signal 301, and 201 shows a system CPU which takes the zoom position from the counter 202, and a focus position from a focus counter, not shown, an iris position, and an extender position. The system CPU 201 combines a video signal from a television camera, not shown, connected to the television lens 100 with a computer graphic image produced in the virtual system 200. At this point, processing is performed such that the computer graphic image matches the video signal from the television camera based on the zoom, focus, iris, and extender position signals input from the television lens 100 as pulse signals with two phases. Both of the images are then combined to complete virtual video without a feeling of strangeness.
FIG. 10 shows the zoom position signal (interface signal) 301 in detail as the pulse signals with two phases which connect the television lens 100 with the virtual system 200.
The digital signals C and D with two phases can be used to calculate relative position data and absolute position data of the zoom lens 105 as shown.
The virtual system 200 in FIGS. 9 and 10 is used in the large television lens. Since the interface signal 301 as the digitized pulse signals with two phases is provided to allow the reliable transmission of the zoom position information without being affected by noise even when the television lens 100 is located far away from the virtual system 200. In addition, the digital encoder 106 of the television lens 100 can have higher resolution to enhance the accuracy in combining the video signal from the television camera with the graphic image.
In the structure shown in FIG. 9, however, the pulse signals with two phases are output from the digital encoder 106 linked with the zoom lens 105, so that the output period of the digital signals with two phases is changed as T1 and T2 shown in FIG. 10 depending on the drive speed of the zoom lens 105. This means that the period of the pulse signals with two phases is so short that the virtual system 200 cannot respond thereto when the digital encoder 106 with high resolution is used to perform high-speed drive.
FIG. 11 shows the structure of a zoom system of a handy-sized lens which is used for a virtual system. In FIG. 11, reference numeral 110 shows a television lens, and 150 shows a drive unit which is mounted on the television lens 110. In FIG. 11, components identical to those in FIG. 9 are designated with the same reference numerals as those in FIG. 9.
While the digital encoder 106 and the counter 120 constitute the digital position detection system in FIG. 9, a potentiometer 109 which outputs an analog signal serves as a position detector of a zoom lens 105 in the structure of FIG. 11. In connection therewith, an operational amplifier 107 and an AD converter 108 are provided. Although not shown, the structures for a focus lens, an iris, and an extender are similar to that of the zoom system.
In the virtual system 200, an operational amplifier 203 for interface matching and an AD converter 204 are provided instead of the counter 202. In the structure described above, a zoom position signal 302 as an interface signal input to the virtual system 200 from the television lens 110 is an analog position signal shown in FIG. 12.
In the structure in which the handy-sized lens is used described above, the zoom position signal 302 as the interface signal is the analog position signal which is sensitive to external noise and may not accurately transmit the position information about the zoom lens, a focus lens and the like in the television lens 110. Another problem is the difficulty in increasing the accuracy of video combination due to permanent noise components.
In addition, the interface signal 302 is a signal regulated on the lens side, and the dedicated operational amplifier and AD converter are necessary for the reception circuit in the virtual system 200 as compared with the pulse signals with two phases. This increases the cost and limits its uses.